Common precursorBiosynthesized from linoleic acidEPA and DHARead d slideImportant reactionsPLA2 and cGlucocorticoid inhibition
StereoisomersCox is not needed for their formationurinary isoprostane levels are used as biomarkers of oxidative stress in ischemic syndrome, reperfusion injury, atherosclerosis, and hepatic disease.
5 lox present in leucocytes
5 lox and FLAPTranscellular biosynthesisSRS ALTB4 can b converted to epoxytetrane by 15 lox
LTB4 is G protein coupled receptor BLT1 and 2 expressed mainly in host defence and inflammation leads to proinflammatorysequalae such as chemotaxis, aggregation and trans migration. LTB4 upregulates the neutrophil function and releases ROS. LTC4 and D4 bind to cys LT1, causes vasoconstriction bronchospasm and increased vascular permeability and plays a imp role is psoriasis arthritis and various inflmatory response.
They oppose chemotaxis transmigration and aggregation, limit eosinophil recruitment, stimulate vasodilation and inhibit the function of NK cels.
Cox 1 functions : renal fuction intestinal mucosal proliferation platelet function antithrombogenesisCox 2 functions : renal adaptation to stress deposition of trabecular bone ovulation placentation uterine contraction
Bergstrom samuelson and vane independentlly obtained pge2 from aa.
Animal studies demonstrate a role for PGE 2 and PGF 2α in early reproductive processes such as ovulation, luteolysis, and fertilization
Aspirin is also effective in dysmenorrhea, but because it has low potency and is quickly hydrolyzed, large doses and frequent administration are necessary. In addition, the acetylation of platelet COX, causing irreversible inhibition of platelet TXA 2 synthesis, may increase the amount of menstrual bleeding
Selective COX-2 inhibitors were developed in an effort to spare gastric COX-1 so that the natural cytoprotection by locally synthesized PGE 2 and PGI 2 is undisturbed. However, this benefit is seen only with highly selective inhibitors and may be offset by increased cardiovascular toxicity.
PGI 2 lowers peripheral, pulmonary, and coronary vascular resistance. It has been used to treat primary pulmonary hypertension as well as secondary pulmonary hypertension, which sometimes occurs after mitral valve surgery. In addition, prostacyclin has been used successfully to treat portopulmonary hypertension, which arises secondary to liver disease.
At birth, reduced PGE 2 levels, a consequence of increased PGE 2 metabolism, allow ductusarteriosus closure. In certain types of congenital heart disease (eg, transposition of the great arteries, pulmonary atresia, pulmonary artery stenosis), it is important to maintain the patency of the neonate’s ductusarteriosus until corrective surgery can be carried out. This can be achieved with alprostadil (PGE 1).
They also stimulate bronchial mucus secretion and cause mucosal edema. Bronchospasm occurs in about 10% of people taking NSAIDs, possibly because of a shift in arachidonate metabolism from COX metabolism to leukotriene formation.
Polymorphisms in the genes for PGD 2 synthase, both DP receptors, and the TP receptor have been linked with asthma in humans. DP antagonists, particularly those directed against DP 2, are being investigated as potential treatments for allergic diseases including asthma.leukotriene-receptor inhibitors (eg, zafirlukast, montelukast ) are effective in asthma. A lipoxygenase inhibitor (zileuton) has also been used in asthma but is not as popular as the receptor inhibitors
Both the medulla and the cortex of the kidney synthesize prostaglandins, the medulla substantially more than the cortex. COX-1 is expressed mainly in cortical and medullary collecting ducts and mesangial cells, arteriolar endothelium, and epithelial cells of Bowman’s capsule. COX-2 is restricted to the renal medullary interstitial cells, the macula densa, and the cortical thick ascending limb.
Expression of medullary COX-2 and mPGES-1 is increased under conditions of high salt intake. COX-2-derived prostanoids increase medullary blood flow and inhibit tubular sodium reabsorption, while COX-1-derived products promote salt excretion in the collecting ducts. Increased water clearance probably results from an attenuation of the action of antidiuretic hormone (ADH) on adenylyl cyclaseIn contrast to the medullary enzyme, cortical COX-2 expression is increased by low salt intake, leading to increased renin release. This elevates glomerular filtration rate and contributes to enhanced sodium reabsorption and a rise in blood pressureHowever, in renal conditions involving inflammatory cell infiltration (such as glomerulonephritis and renal transplant rejection), the inflammatory cells (monocyte-macrophages) release substantial amounts of TXA 2. Theoretically, TXA 2 synthase inhibitors or receptor antagonists should improve renal function in these patients, but no such drug is clinically available.
Endogenous pyrogens release interleukin-1, which in turn promotes the synthesis and release of PGE 2. Aspirin and other antipyretic compounds block this synthesis
Prostaglandins may mediate the effects of mechanical forces on bones and changes in bone during inflammation. EP 4 -receptor deletion and inhibition of prostaglandin biosynthesis have both been associated with impaired fracture healing in animal models
There has been significant interest in the role of prostaglandins, and in particular the COX-2 pathway, in the development of malignancies. Pharmacologic inhibition or genetic deletion of COX-2 restrains tumor formation in models of colon, breast, lung, and other cancers. Large human epidemiologic studies have found that the incidental use of NSAIDs is associated with significant reductions in relative risk for developing these and other cancersDespite the support for COX-2 as the predominant source of oncogenic prostaglandins, randomized clinical trials have not been performed to determine whether superior anti-oncogenic effects occur with selective inhibition of COX-2, compared with nonselective NSAIDs. Indeed data from animal models and epidemiologic studies in humans are consistent with a role for COX-1 as well as COX-2 in the production of oncogenic prostanoids.Augmented expression of mPGES-1 is evident in tumors, and preclinical studies support the potential use of mPGES-1 inhibitors in chemoprevention or treatment.Studies in mice lacking EP 1 , EP 2 , or EP 4 receptors confirm reduced disease in multiple carcinogenesis models. EP 3 , in contrast, plays no role or may even play a protective role in some cancers. Transactivation of epidermal growth factor receptor (EGFR) has been linked with the oncogenic activity of PGE
Lox metabolites also have endocrine effects 12HETE stimulate the release of aldosterone from adrenal cortex
New style prostaglandins
Therapeutic uses of
Dr. Vaneet Aggarwal
Classification of Autacoids
Therapeutic Effects and Uses
are substances that are rapidly synthesized in
response to specific stimuli act quickly in the immediate
environment and remain active for only a short time
In the cell arachidonic acid does not exist as a free fatty
acid but rather is esterified to sn2 position of membrane
phospholipids predominantly phosphatidylcholine and
Arachidonic acid is released from cellular phospholipids
by the enzyme phospholipase A2 which hydrolyse Acyl
Phospholipids esterified arachidonic acid is susceptible
to free radical mediated peroxidation and release of
these modified lipids from the phospholipids by
phospholipase A2 give rise to Isoprostanes .
Two Isoprostanes in particular 8-epi-PGF2α and 8-epiPGE2 are potent vasoconstrictors.
Because the rate of formation of Isoprostanes depend
on cellular oxidative conditions, Isoprostanes levels
may be indicative of oxidative stress in a wide range of
Specific isozymes of microsomal cytochrome P450
monooxygenases convert AA to hydroxy- or
The products are 20-HETE, generated by the CYP
hydroxylases (CYP3A, 4A, 4F) and the 5,6-, 8,9-,
11,12-, and 14,15-epoxyeicosatrienoic acids (EETs),
which arise from the CYP epoxygenase (2J, 2C).
The biologic actions of the EETs are reduced by their
conversion to the corresponding, and biologically less
active, dihydroxyeicosatrienoic acids (DHETs) through
the action of soluble epoxide hydrolase (sEH).
Besides the COX pathway the other major fate of the
arachidonic acid is Lipoxygenase pathway which leads
to the formation of leukotrienes and lipoxins.
Lipoxygenases are enzymes that catalyze the insertion
of molecular oxygen into arachidonic acid using non
haeme iron to generate specific hydroperoxides.
Three Lipoxygenases; i.e, 5- Lipoxygenase, 12Lipoxygenase and 15- Lipoxygenase are the major
LOX isoforms found in humans
The enzyme LTA4 hydrolase converts LTA4 to LTB4 in
neutrophils and erythrocytes.
LTA4 conversion to LTC4 occurs in mast cells, basophils
, eosinophils and macrophages by the addition of
LTC4 , LTD4 , LTE4 , LTF4 which represents the cysteinyl
leukotrienes are inter converted by removal of amino
acids portion of gamma-glutamylcysteinylglycine
Lipoxins (lipoxigenase interaction products) are
derivatives of arachidonic acid containing four
conjugated double bonds and three hydroxyl groups.
The two main lipoxins , LXA4 and LXB4 modulate the
actions of leukotrienes and cytokines and are important
in resolution of inflammation.
At the site inflammation there is typically an inverse
relationship between the amount of lipoxin and
Cyclooxygenase are glycosylated homodimeric, membrane bound
haeme containing enzymes that are ubiquitous in animal cells from
invertebrates to humans.
Two cyclooxygenase iso forms , denoted COX1 and COX2 are
found in humans .
Protein kinetics studies suggest that there may be a third
functional cyclooxygenase isoform COX3 which appears to be
expressed primarily in the central nervous system, may be a
potential site of action of acetaminophen.
Each COX catalyses two sequential reactions. The first
reaction, the COX step, is the oxygen dependent cyclization of
arachidonic acid to prostaglandin G2 (PGG2); the second reaction
, the peroxidase step , is the reduction of PGG2 to PGH2.
The constitutively expressed COX1 is believed to
function in physiological, or housekeeping activities
such as vascular homeostatsis, maintenance of renal
and gasterointestinal blood flow etc.
A number of as needed or specialized functions are
attributed to the products of the inducible COX2
enzyme including roles in
inflammation, fever, pain, transduction of painful stimuli
in the spinal cord etc.
Thromboxanes And Prostacyclins
Platelets express high level of the enzyme
thromboxane synthase but do not contain prostacyclin
synthase. Therefore TxA2 is the chief eicosanoid
product of platelets.
In contrast the vascular endothelium lacks
thromboxane synthase but expresses a prostacyclin
synthase. Therefore PGI2 is the primary eicosanoid
product of vascular endothelium.
The local balance between TxA2 and PGI2 levels is
critical in the regulations of systemic blood pressure
and Thrombogenesis. Imbalances can lead to
hypertension, ischemia, thrombosis, coagulopathy, myo
cardial infarction and stroke.
Prostoglandins are a large family of structurally similar
compounds that have potent and specific biological
History of Prostaglandins :
In 1930, Kurzrok and Leib demonstrated the activity of
human semen on isolated strips of human uterine
This was conformed by Von Euler (1935) who
demonstrated a substance present in the extracts of
human seminal fluid, which caused contraction of the
isolated intestine and uterine muscles and
vasodilation.(Nobel Prize 1970)
This substance was named prostaglandin because of
its probable origin from the prostate. Bergstrom (Nobel
Prize 1982) and associates showed that various PG’s
are closely related derivatives of the lipid soluble
Major Site(s) of
Major Biological Activities
inhibits platelet and leukocyte aggregation, decreases T-cell
proliferation and lymphocyte migration and secretion of IL1&ALPHA; and IL-2; induces vasodilation and production of cAMP
increases vasodilation and cAMP production, enhancement of the
effects of bradykinin and histamine, induction of uterine
contractions and of platelet aggregation; decreases T-cell
proliferation and lymphocyte migration and secretion of IL1&ALPHA; and IL-2
kidney, spleen, increases vasoconstriction, bronchoconstriction and smooth muscle
inhibits platelet and leukocyte aggregation, decreases T-cell
proliferation and lymphocyte migration and secretion of ILendothelial cells
1&ALPHA; and IL-2; induces vasodilation and production of cAMP
induces platelet aggregation, vasoconstriction, lymphocyte
proliferation and bronchoconstriction
a short-lived precursor to thromboxanes A2 and B2, induction of
platelet aggregation and vasoconstriction
First, stable oral or parenteral long-acting analogs of
the naturally occurring prostaglandins have been
Second, enzyme inhibitors and receptor antagonists
have been developed to interfere with the synthesis or
effects of the eicosanoids.
Third, efforts at dietary manipulation—to change the
polyunsaturated fatty acid precursors in the cell
membrane phospholipids and so change eicosanoid
synthesis—is used extensively in over-the-counter
products and in diets emphasizing increased
consumption of cold water fish.
PGF 2α, TXA 2, and low concentrations of PGE 2
contract uterine muscle.
PGI 2 and high concentrations of PGE 2 cause
PGF 2α, together with oxytocin, is essential for the
onset of parturition.
PGE 2 and PGF 2α have potent oxytocic actions. The ability of
the E and F prostaglandins and their analogs to terminate
pregnancy at any stage by promoting uterine contractions has
been adapted to common clinical use.
The drugs are used for first- and second-trimester abortion and for
priming or ripening the cervix before abortion.
These prostaglandins appear to soften the cervix by increasing
proteoglycan content and changing the biophysical properties of
Dinoprostone, a synthetic preparation of PGE 2, is administered
vaginally for oxytocic use.
It is approved for inducing abortion in the second trimester of
pregnancy, for missed abortion, for benign hydatidiform mole, and
for ripening of the cervix for induction of labor in patients at or near
Dinoprostone stimulates the contraction of the uterus
throughout pregnancy. As the pregnancy
progresses, the uterus increases its contractile
response, and the contractile effect of oxytocin is
potentiated as well.
Antiprogestins (eg, mifepristone) have been combined
with an oral oxytocic synthetic analog of PGE
1(misoprostol) to produce early abortion.
An analog of PGF 2α is also used in obstetrics. This
drug, carboprost tromethamine is used to induce
second-trimester abortions and to control postpartum
hemorrhage that is not responding to conventional
methods of management.
Facilitation of labor:
Numerous studies have shown that PGE 2, PGF 2α
, and their analogs effectively initiate and stimulate
labor, but PGF 2α is one tenth as potent as PGE 2 .
PGF 2α is a bronchoconstrictor and should be used
with caution in women with asthma
PGE 2 and PGF 2α should be superior to oxytocin for
inducing labor in women with preeclampsia-eclampsia
or cardiac and renal diseases because, unlike
oxytocin, they have no antidiuretic effect. In
addition, PGE 2 has natriuretic effects.
Primary dysmenorrhea is attributable to increased
endometrial synthesis of PGE 2 and PGF 2α during
menstruation, with contractions of the uterus that lead
to ischemic pain. NSAIDs successfully inhibit the
formation of these prostaglandins and so relieve
dysmenorrhea in 75–85% of cases
Testosterone promotes prostaglandin production.
Thromboxane and leukotrienes have not been found in
Men with a low seminal fluid concentration of
prostaglandins are relatively infertile.
Smooth muscle-relaxing prostaglandins such as PGE 1
enhance penile erection by relaxing the smooth muscle
of the corpora cavernosa.
Intracavernosal injection or urethral suppository therapy with
alprostadil (PGE 1) is a second-line treatment for erectile
Doses of 2.5–25 mcg are used.
Penile pain is a frequent side effect, which may be related to
the algesic effects of PGE derivatives; however, only a few
patients discontinue the use because of pain.
Prolonged erection and priapism are side effects that occur
in less than 4% of patients and are minimized by careful
titration to the minimal effective dose.
When given by injection, alprostadil may be used as
monotherapy or in combination with either papaverine or
GIT: Longitudinal muscle is contracted by PGE 2 (via EP
3) and PGF 2α (via FP), whereas circular muscle is
contracted strongly by PGF 2α and weakly by PGI
2, and is relaxed by PGE 2 (via EP 4).
Administration of either PGE 2 or PGF 2α results in
In the stomach PGE2 and PGI2 contribute to increased
mucus secretion, and reduced pepsin content.
Misoprostol is an orally active synthetic analog of PGE
1. The FDA-approved indication is for prevention of
NSAID-induced peptic ulcers.
The drug is administered at a dosage of 200 mcg four
times daily with food.
This and other PGE analogs (eg, enprostil) are
cytoprotective at low doses and inhibit gastric acid
secretion at higher doses.
Misoprostol use is low, probably because of its adverse
effects including abdominal discomfort and occasional
Dose-dependent bone pain and hyperostosis have been
described in patients with liver disease who were given
long-term PGE treatment
Low concentrations of PGE 2 enhance (via EP
3), whereas higher concentrations inhibit (via
IP), platelet aggregation.
Both PGD 2 and PGI 2 inhibit aggregation
via, respectively, DP 1 and IP-dependent elevation in
TXA 2 is the major product of COX-1, the only COX
isoform expressed in mature platelets. It induces shape
change through G12/G13 mediated Rho-Rho kinase
dependent regulation of myosin light-chain
phosphorylation and aggregation through Gq
dependent activation of PKC.
Eicosanoids are involved in thrombosis because TXA 2
promotes platelet aggregation while PGI 2 , and
perhaps also PGE 2 and PGD 2 , are platelet
TXA 2, in addition to activating platelets, amplifies the
response to other platelet agonists; hence inhibition of
its synthesis inhibits secondary aggregation of platelets
induced by adenosine diphosphate, by low
concentrations of thrombin and collagen, and by
In most vascular beds PGE2, PFI2, and PGD2 elicit
vasodilation and drop in blood pressure.
PGE2 can cause vasoconstriction through activation of EP1
and EP3 receptors.
Infusion of PGD2 results in flushing, nasal stuffiness and
PGI2 relaxes vascular smooth muscle causing hypotension
and reflex tachycardia on I.V. administration.
PGF2α does not alter blood pressure .
Cardiac output is generally is increased by infusion of PGs
of E and F series.
LTC4 and LTD4 results in hypotension.
PGI 2 (epoprostenol) approved for treatment of primary
pulmonary hypertension improves symptoms, prolongs
survival, and delays or prevents the need for lung or lungheart transplantation.
Side effects include flushing, headache, hypotension,
nausea, and diarrhea. The extremely short plasma half-life
(3–5 minutes) of epoprostenol necessitates continuous
intravenous infusion through a central line for long-term
treatment, which is its greatest limitation.
Iloprost (half-life about 30 minutes) is usually inhaled six to
nine times per day, although it has been delivered by
intravenous administration outside the USA.
Treprostinil (half-life about 4 hours) may be delivered by
subcutaneous or intravenous infusion.
Peripheral Vascular disease
PGE1 or PGI2 infused i.v. can promote ulcer healing in
acute intermittent claudication.
Beraprost is a stable oral PGI2 derivative which is given
thrice a day for treating peripheral vascular disease.
To reduce infarct size: intravenous infusion of PGI2 Iloprost
in the immediate post MI period can help reducing the infarct
size but efficacy is doubtful.
A number of studies have investigated the use of PGE 1
and PGI 2 compounds in Raynaud’s phenomenon and
peripheral arterial disease. However, these studies are
mostly small and uncontrolled, and these therapies do not
have an established place in the treatment of peripheral
Patent Ductus Arteriosus
Patency of the fetal ductus arteriosus depends on COX-2derived PGE 2 acting on the EP 4 receptor.
Adverse effects include
apnea, bradycardia, hypotension, and hyperpyrexia.
Because of rapid pulmonary clearance (the half-life is about
5–10 minutes in healthy adults and neonates), the drug
must be continuously infused at an initial rate of 0.05–0.1
mcg/kg/min, which may be increased to 0.4 mcg/kg/min.
Prolonged treatment has been associated with ductal
fragility and rupture.
In delayed closure of the ductus arteriosus, COX inhibitors
are often used to inhibit synthesis of PGE 2 and so close the
ductus. Premature infants in whom respiratory distress
develops due to failure of ductus closure can be treated with
a high degree of success with indomethacin.
Although PGF2αinduces constriction of the iris
sphincter muscle, its overall effect is lower intraocular
pressure by increased outflow of aqueous humor from
the anterior chamber via the uveoscleral pathway and
trabecular meshwork pathway.
A variety of FP receptors agonists have proven
effective in the treatment of open angle glaucoma, a
condition associated with loss of COX2 expression in
the pigment epithelium of the ciliary body.
Latanoprost, a stable long-acting PGF2α derivative,
was the first prostanoid used for glaucoma.
The success of latanoprost has stimulated
development of similar prostanoids with ocular
hypotensive effects, and bimatoprost, travoprost, and
unoprostone are now available.
These drugs act at the FP receptor and are
administered as drops into the conjunctival sac once or
Adverse effects include irreversible brown pigmentation
of the iris and eyelashes, drying of the eyes, and
Respiratory smooth muscle is relaxed by PGE 2 and
PGI 2 and contracted by PGD 2, TXA 2, and PGF 2α.
The cysteinyl leukotrienes are also
bronchoconstrictors. They act principally on smooth
muscle in peripheral airways and are a thousand times
more potent than histamine, both in vitro and in vivo.
PGE 2 is a powerful bronchodilator when given in aerosol form.
Unfortunately, it also promotes coughing, and an analog that
possesses only the bronchodilator properties has been difficult to
PGF 2α and TXA 2 are both strong bronchoconstrictors and were
once thought to be primary mediators in asthma.
The cysteinyl leukotrienes—LTC 4, LTD 4 , and LTE 4 —probably
dominate during asthmatic constriction of the airways.
Corticosteroids and cromolyn are also useful in asthma.
Corticosteroids inhibit eicosanoid synthesis and thus limit the
amounts of eicosanoid mediator available for release. Cromolyn
appears to inhibit the release of eicosanoids and other mediators
such as histamine and platelet-activating factor from mast cells.
The major renal eicosanoid products are PGE 2 and PGI
2, followed by PGF 2α and TXA 2. The kidney also
synthesizes several hydroxyeicosatetraenoic
acids, leukotrienes, cytochrome P450 products, and
Prostaglandins play important roles in maintaining blood
pressure and regulating renal function, particularly in
marginally functioning kidneys and volume-contracted
PGE 2 and PGI 2 maintain renal blood flow and glomerular
filtration rate through their local vasodilating effects. These
prostaglandins also modulate systemic blood pressure
through regulation of water and sodium excretion.
PGE 2 is thought to stimulate renin release through
activation of EP 4 or EP 2.
PGI 2 can also stimulate renin release and this may be
relevant to maintenance of blood pressure in volumecontracted conditions and to the pathogenesis of
TXA 2 causes intrarenal vasoconstriction (and perhaps an
ADHlike effect), resulting in a decline in renal function. The
normal kidney synthesizes only small amounts of TXA 2
Hypertension is associated with increased TXA 2 and
decreased PGE 2 and PGI 2 synthesis in some animal
PGF 2α may elevate blood pressure by regulating renin
release in the kidney.
Increased biosynthesis of prostaglandins has been
associated with one form of Bartter’s syndrome.
This is a rare disease characterized by low-to-normal
blood pressure, decreased sensitivity to
angiotensin, hyperreninemia, hyperaldosteronism, and
excessive loss of K +. There also is an increased
excretion of prostaglandins, especially PGE
metabolites, in the urine.
After long-term administration of COX
inhibitors, sensitivity to angiotensin, plasma renin
values, and the concentration of aldosterone in plasma
return to normal. Although plasma K + rises, it remains
low, and urinary wasting of K + persists
Inflammation and Immunity
PGE 2 and PGI 2 are the predominant prostanoids
associated with inflammation.
Both markedly enhance edema formation and
leukocyte infiltration by promoting blood flow in the
PGE 2 and PGI 2, through activation of EP 2 and
IP, respectively, increase vascular permeability and
PGE 2 and TXA 2 may play a role in T-lymphocyte
development by regulating apoptosis of immature
Inflammation and Immunity
PGE 2 suppresses the immunologic response by inhibiting
differentiation of B lymphocytes into antibody-secreting
plasma cells, thus depressing the humoral antibody
It also inhibits cytotoxic T-cell function, mitogen-stimulated
proliferation of T lymphocytes, and the release of cytokines
by sensitized TH1 lymphocytes.
PGD2 a major product of mast cells, is a potent
chemoattractant for eosinophils in which it also includes
degranulation and leukotriene biosynthesis
PGD 2 also induces chemotaxis and migration of TH 2
lymphocytes mainly via activation of DP 2 , although a role
for DP 1 has also been established.
Cell mediated Organ Transplant Rejection
Administration of PGI 2 to renal transplant patients has
reversed the rejection process in some cases.
Experimental in vitro and in vivo data show that PGE 2 and
PGI 2 can attenuate T-cell proliferation and rejection, which
can also be seen with drugs that inhibit TXA 2 and
In organ transplant patients, urinary excretion of metabolites
of TXA 2 increases during acute rejection.
Corticosteroids, the first line drugs used for treatment of
acute rejection because of their lymphotoxic effects, inhibit
both phospholipase and COX-2 activity.
COX-2 appears to be the form of the enzyme most
associated with cells involved in the inflammatory
COX-1 also contributes significantly to prostaglandin
biosynthesis during inflammation.
Aspirin and other anti inflammatory agent that inhibit
cox are used for inflammation.
immune complexes are deposited in the affected
joints, causing an inflammatory response that is
amplified by eicosanoids.
Lymphocytes and macrophages accumulate in the
synovium, whereas leukocytes localize mainly in the
The major eicosanoids produced by leukocytes are
leukotrienes, which facilitate T-cell proliferation and act
Human macrophages synthesize the COX products
PGE2 and TXA2 and large amounts of leukotrienes.
Central and Peripheral Nervous System
Fever: PGE 2 increases body temperature,
predominantly via EP 3 , although EP 1 also plays a
role, especially when administered directly into the
Exogenous PGF 2α and PGI 2 induce fever, whereas
PGD 2 and TXA 2 do not .
Sleep: When infused into the cerebral ventricles, PGD
2 Induces natural sleep via activation of DP 1
PGE 2 infusion into the posterior hypothalamus causes
Central and Peripheral Nervous System
PGE compounds inhibit the release of norepinephrine
from postganglionic sympathetic nerve endings
PGE 2 and PGI 2 sensitize the peripheral nerve
endings to painful stimuli by increasing their terminal
membrane excitability. Prostaglandins also modulate
PGE 2, and perhaps also PGD 2, PGI 2, and PGF 2α,
contribute to so-called central sensitization, an increase
in excitability of spinal dorsal horn neurons, that
augments pain intensity, widens the area of pain
perception, and results in pain from normally Innocuous
Prostaglandins are abundant in skeletal tissue and are
produced by osteoblasts and adjacent hematopoietic cells.
The major effect of prostaglandins (especially PGE 2, acting
on EP 4 ) in vivo is to increase bone turnover, ie, stimulation
of bone resorption and formation.
COX inhibitors can also slow skeletal muscle healing by
interfering with prostaglandin effects on myocyte
proliferation, differentiation, and fibrosis in response to
Prostaglandins may contribute to the bone loss that occurs
at menopause; it has been speculated that NSAIDs may be
of therapeutic value in osteoporosis and bone loss
prevention in older women.
PGE 2, which is considered the principal oncogenic
prostanoid, facilitates tumor initiation, progression, and
metastasis through multiple biologic effects, increasing
proliferation and angiogenesis, inhibiting
apoptosis, augmenting cellular invasiveness, and
TXA 2 emerging as another likely procarcinogenic
mediator, deriving either from macrophage COX-2 or
Several species shows the systemic administration of
PGE2 increasing the circulating concentrations of
adrenocorticotropic hormone (ACTH), growth hormone,
prolactin, and gonadotropins.
Stimulation of steroid production by the adrenals,
stimulation of insulin release, and thyrotropin-like effects
on the thyroid.
The critical role of PGF2α in parturition relies on its ability
to induce an oxytocin-dependent decline in progesterone
PGE2 works as positive-feedback loop to induce oocyte
maturation required for fertilization during and after
Because arachidonic acid is derived from dietary
linoleic and α-linolenic acids, which are essential fatty
acids, the effects of dietary manipulation on arachidonic
acid metabolism have been extensively studied.
The first adds corn, safflower, and sunflower oils, which
contain linoleic acid (C18:2), to the diet.
The second approach adds oils containing
eicosapentaenoic (C20:5) and docosahexaenoic acids
(C22:6), so- called omega-3 fatty acids, from cold-water